It is a kind of viscoelastic foam, also called memory sponge. The product can be designed and moulded on the basis of ergonomics, i.e., the most uniform load bearing capacity is provided to dove-tail with the head-neck curve based on the natural outspread status of the head and neck when in sleep, so as to enable the head and neck to relax and at ease, thus eliminating the fatigue and aching pain resulting from incorrect lying posture.